Trump suggested Republican rules for awarding the nomination based on a majority of delegates should be jettisoned. “I think that whoever gets the most delegates should win,” he said.

Neither Rubio nor Ohio governor John Kasich would admit the extreme narrowness of his path to the nomination. “Math doesn’t tell the whole story in politics,” Kasich said.

Rubio dismissed a human role in climate change : “Sure, the climate is changing,” he said. “There was never a time when the climate was not changing.”

Asked about violence at his rallies , Trump said he did not condone it, but his supporters “have anger that’s unbelievable”. “They love this country,” he said. “They don’t like seeing bad trade deals.”